As a film forming process, various processes, such as a vacuum vapor deposition process, a sputtering process and an ion plating process, have been developed. A laminate obtained by such a film formation process is widely utilized in production of display devices, such as liquid crystal displays or organic EL displays, semiconductor devices, etc. In the display devices, the semiconductor devices, etc., the laminate is usable as a protective film, and various types of functional films, such as an optical filter and an anti-reflection film.
Late years, demand for device units using the functional films, such as a LCD (Liquid Crystal Display) TV, a mobile phone and a video game machine, has been rapidly expanded. Along with expansion of the demand, it has become an urgent matter to develop a technique for mass-producing a functional film within a short period of time. In order to respond to this need, a roll-to-roll technique has been developed. The roll-to-roll technique is designed to feed an elongated substrate wound in a roll form, between two rolls, so as to enable continuous film formation, thereby enhancing efficiency of a film formation operation.
However, mass production based on the conventional unsophisticated roll-to-roll technique has limitations. Moreover, a layered structure required for a functional film is likely to vary depending on the type of device to which the functional film is applied, performance required for the functional film, etc. Thus, there is a need for developing a flexible film formation method capable of producing various laminate structures within a short period of time and in an easy and low-cost manner.
One example of a film formation method using a roll-to-roll technique is disclosed in JP 4415584B (Patent Document 1). In this film formation method, one rotary drum is provided between two rolls, and a plurality of targets are arranged with respect to the one rotary drum which is transporting a substrate, to enable continuous film formation, thereby enhancing efficiency of the film formation operation.
JP 2010-236076A (Patent Document 2) and JP 07-098854A (Patent Document 3) disclose a film formation method capable of subjecting both sides of a substrate to film formation, using a roll-to-roll technique. In this film formation method, to enable double-side film formation, two rotary drums and one take-up roll located between the rotary drums are used, wherein a roll fed from a feed roll is subjected to film formation through the two rotary drums which are rotating in respective opposite directions, and then rolled up on the take-up roll.